You might be careful here. I recently heard that over 90% of prescription eyeglasses bought online were made wrong or "out of standard," but after talking to this girl at WalMart today, online sounds good! She told me that Polycarbonate means that it is "Scratch Proof." In reality, poly is very shatter resistant but soft and without a good Scratch coating actually scratches easier. She also told me that you cannot get RX sunglasses unless you buy a polarized lens...they don't give you a choice. Lord, I hope uneducated pilots don't buy their suns at here, they won't be able to see the instrument panel! Lastly, I was told that Progressive bifocals ran from $225 to $500 and that the difference was that in the $500 one "your prescription takes up the whole lens" where as in the cheaper one you can only see "through the middle." Sounds like at WalMart the opticians are 1) definitely not certified and 2) may have been stacking tires the day before. These are your eyes, folks! Ouch!